According to a post by Bornakk, Arena Season 6 could end as early as Tuesday, Aug. 25, which is in less than two weeks. The process to determine eligibility for end-of-season rewards should take about one week. Bornakk warns that players who may be eligible for titles or Furious Gladiator's Frostwyrm shouldn't transfer to another server until Season 6 is over.
Season 7 won't begin until at least one week after the sixth season comes to a close. Team ratings, personal ratings and arena points will be wiped once the seventh season begins in early September. Between seasons, you'll be able to practice with skirmishes.